JPS6137829A - Production of electroconductive plastic foam - Google Patents

Abstract

PURPOSE:To heighten the expansion ratio of a polyolefin resin foam, by adding a higher fatty acid triglyceride in the production of an electroconductive plastic foam by adding carbon black to a polyolefin resin and extrusion-foaming the mixture. CONSTITUTION:90-70wt% polyolefin resin selected from among polyethylene, polypropylene, polybutene-1, ethylene/vinyl acetate copolymer and a mixture thereof is mixed with 10-30wt% carbon black. 100pts.wt. resulting mixture is further mixed with 0.1-10pts.wt. higher fatty acid triglyceride (e.g., stearic acid triglyceride or hardened soybean oil) and, optionally, a blowing agent (e.g., butane or flon), a nucleating agent, etc., and extrusion-foamed to obtain the purpose electroconductive plastic foam.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing a tetraelectric plastic foam, and more specifically, the present invention relates to a method for producing a tetraelectric plastic foam, and more specifically,
The present invention relates to a method for producing plastic foam suitable for packaging objects such as precision instruments, electrical parts, or electronic parts that must be protected from dust.

[Technical background and explanation of conventional technology]

Plastic foam has appropriate elasticity and is highly flexible, so it can be used for items that are easily stiffened, expensive items, etc. - is widely used in packaging various items and as a spacer between these items to prevent the packaged items from coming into contact with each other or being crushed. Plastic foam has a very high electrical resistance and is a strong insulator, so it is easily charged with static electricity. For this reason, plastic foam tends to attract dust and is not only unsuitable as a packaging material, but also IC, transistors, capacitors, electronic parts using these, and 7tt for fJ4. In many cases, it becomes practically impossible to use crystals for packaging purposes such as personal items, cameras or audio equipment.

Until now, plastic foam has been developed to reduce its electrical insulation properties, reduce the electrical insulation to 4 volts, prevent static electricity, and thereby prevent dust from accumulating. Attempts have been made to apply antistatic II agents to plastic foams, and to incorporate carbon black into plastic foams (Special Part 1), 1973, 403.
Publication No. 26, JP-A-58-1792 old issue, JP-A-58-1792
8-1! '185:37 Publication, JP-A-58-1 (18
5+48 Bow Publication). In addition, the poly-1-1 NOFINE-based resin blended with 11 carphone blacks is able to absorb the gas necessary for foaming.
1: Since it is difficult to maintain the poly-1 Nophine-based tree 1, carbon black and aluminum 1''' are used.
Attempts have also been made to reduce the internal resistance value of conductive foam by adding a compound (Japanese Patent Application Laid-Open No.
8-80'12 Bow Publication), the present inventors have found that by combining higher fatty acid l-lyclycerai 1- with polyolefin resin, the volume change is small after extrusion molding of the foam. A method for manufacturing polyolefin foam was developed (Japanese Patent Publication No. 30898/1989).

[Problems to be solved by the invention]

The present inventors attempted to mix carbon black into raw material plastics and perform extrusion foam molding in order to reduce the electrical insulation properties and improve the conductivity of plastic foams. , to the extent that it does not charge static electricity (1
In order to obtain a conductivity of surface internal resistance at an interval of 0 ohms (= 10 ohms), at least 30% (by weight) of carbon black must be added to the raw material plastic. When the blended product is extruded and foam-molded, the expansion ratio of the plastic foam decreases, and the mechanical strength of the plastic foam also decreases. We encountered the problem that it became difficult to use as a plastic foam, and we conducted repeated research with the aim of improving this point.When we added higher fatty acid tricrycerite to the raw material mixture for plastic foam, we found that it became difficult to use it as a plastic foam. 4 [Despite containing a large amount of carbon black, the expansion ratio of the plastic foam can be improved, the mechanical strength of the plastic foam can be maintained, and the conductive performance of the plastic foam can be improved. Based on this finding, we have arrived at the present invention.

[Objective of the present invention does not include carbon black]
The foaming ratio does not decrease, and the machine n (1 strength is maintained,
Furthermore, it is an object of the present invention to provide a method for producing a conductive plastic foam having improved conductive performance and reduced static electricity charging.

1. Means for Solving Problem 1] The present invention provides a method for producing a conductive plastic foam consisting of a foamable raw material mixture of plasti-sox, which is blended with carbon black, and is extruded and foam-molded.
A ratio of 90 to 70% (city@) of polyolefin-based wood and 10 to 30% (superposition) of carbon black is added to the raw material mixture containing the lever, from 0.1 to 100 parts by weight of the raw material mixture. This is a method for producing a conductive plastic foam, which is characterized by mixing 10 parts of higher fatty acid tricleide and foaming the mixture.

According to the present invention, polyolefin resin, carbon black, and higher fatty acid tricrycerite are combined into 90 to 70% of polyolefin resin, 910 to 910 parts of Carpump 5
30 parts by weight and higher fatty acid 1 to liqueceride O61
~10 Mfa parts are mixed to prepare the raw materials and blends, but if necessary, additives such as nucleating agents and blowing agents may be further mixed in the preparation of the raw material blends. I can do it. The raw material mixture thus obtained is foam-molded by a conventional method. When a volatile foaming agent such as butane or chlorofluorocarbon is used as a foaming agent, in the molding machine for foam-molding, It can also be added to the raw material mixture, stirred and mixed well, and then foam-molded. Foam molding may be carried out by any conventional foam molding method such as extrusion 1y foam molding or press foam molding. As the nucleating agent, finely powdered inorganic powder such as talc can be used.

In producing the electrically conductive plastic foam according to the present invention, the high n-fatty acid tricrycerite is mixed with:
It may be carried out at any time during the preparation of the foamable raw material mixture, and it can also be carried out in an extrusion molding machine during foam molding of the foamable raw material mixture. Higher fatty acid 1-lyclyceride contains 70 to 90% (by weight) polyolefin type [flJ and 10 to 30% (by weight) carbon black], polyolefin type H and carbon black. It is used in a ratio of 0.1 to 10 parts by weight per 100 parts by weight of the raw material mixture.

When the amount of higher fatty acid tricrycerite is less than 0.1 part by weight, it is difficult to impart sufficient electrical conductivity (surface resistivity of about 10 ohms) to the plastic foam product. If the amount is more than 10 parts by weight, a phenomenon called whitening of the surface of the conductive plastic foam product may occur. Usually, the higher fatty acid triglyceride is preferably used in an amount of 0.3 to 7 parts by weight per 100 parts by weight of the raw material mixture containing the polyolefin resin and carbon black.

The foamable raw material mixture for extrusion foam molding includes ingredients added to the foamable raw material mixture used in the production of general plastic foams, such as talc or silica powder, Foaming nucleating agents such as azodicarbonamide or other decomposable organic blowing agents, N or CO gas or mixtures thereof, spreading agents such as polybutene or polyethylene glycol, butane, chlorofluorocarbons, and methyl chloride. or a mixture thereof, or a crosslinking agent such as peroxide in the case of cross-section foam molding, can be deeply mixed into the raw material mixture as required.

In some cases, it is also possible to irradiate a non-strength plastic foam made by foam molding with radiation to form overhead wires.

As the polyolefin resin in the raw material mixture of the present invention, any resin that can be used to produce plastic foam can be used, but usually polyethylene, polypropylene, polybutene, etc. ], copolymers of these olefins with other vinyl monomers such as vinyl acetate, vinyl chloride, acrylic acid or methacrylic acid, or mixtures thereof are used. Among these, it is preferable to use ethylene-vinyl acetate copolymer.

As the carbon black in the raw material formulation of the present invention, since ordinary carbon black has conductivity, any stiff material can be used.
It is preferable to use carbon black having a large specific surface area and high conductivity, such as Ketjen black (manufactured by Lion Akzo).

As the higher fatty acid triglycerite in the raw material composition of the present invention, triglycerides of saturated fatty acids having 12 to 20 carbon atoms are used, and animal fats and oils such as beef tallow, pig intestine or whale oil, soybean oil, olive oil, and cacao butter are used. Hydrogenated oils obtained by hydrogenation of vegetable oils such as , cottonseed oil, castor oil, rapeseed oil, coconut oil or corn oil can also be used.

Among the fatty acid components of these higher fatty acid tricrycerites, stearic acid, palmitic acid, and C″X, which is a mixture thereof, are preferable.

An example of implementation of the present invention and an example of comparison will be described below, but the present invention is not limited to these examples.

Examples 1 to 4 (Preparation of raw material pellets) Ethylene-vinyl acetate copolymer [melt index:
2゜0, density: 0゜940, vinyl acetate content: 20% (
weight)], carbon black [Ketjenblack EC
(registered trademark)], beef tallow hydrogenated oil, and talc in the amounts shown in Table 1, put them into a super mixer, mix them, put the mixture into an extruder, and extrude it linearly from a circular nozzle with three diameters. , three lengths were cut to obtain raw material pellets containing carbon black.

(Preparation of foamed sheet) Raw material pellets were fed into the hopper of an extrusion molding machine equipped with an annular extrusion nozzle (diameter 30 mm) at 1 OK9/hr, heated to 200°C, and liquefied butane was
After press-fitting and mixing well at 1.5Kg/hr,
A foamed sheet was obtained by extrusion into the cooled atmosphere from an annular nozzle of an extruder.

The density and surface resistivity of the foamed sheet were as shown in Table 1.

Comparative Examples 1 to 2 (Preparation of raw material pellets) The ethylene-vinyl acetate copolymer, carbon black, and talc used in the examples were used in the amounts shown in Table 1, and treated in the same manner as in the examples. Raw material pellets were obtained.

(Preparation of foamed sheet) Raw material pellets 1 to 1 were treated in the same manner as in Example to obtain foamed sheet No. 11. The density and surface resistivity of the foamed sheet were as follows.
It was as shown in the table.

(The following is a blank space) 12) (Measurement of surface resistivity) On the surface of the foam sheet, terminals were brought into contact with the foam sheet at intervals of 1 Gmm, and the electrical resistance value at the intervals was measured.

According to a comparison between Examples 1 and 2 and Comparative Example 2, and Examples 3 and 4 and Comparative Example 1, by blending a small amount of hardened beef tallow oil into the raw material, the surface resistivity of the foam sheet was reduced and the conductivity was improved. It can be seen that sexual performance improves.

〔Effect of the invention〕

According to the present invention, by blending higher fatty acid triglyceride with polyolefin resin, a sufficient expansion ratio of the foamed plastic sheet can be maintained by blending only a small amount of carphone black, thereby imparting sufficient electrical conductivity. can do.

Claims (2)

[Claims] (1) In a method for producing a conductive plastics foam, which comprises blending carbon black into a plastics foamable raw material mixture and extruding and foam-molding the mixture,
~30% (by weight) carbon black and 90-70
% (by weight) of a polyolefin resin, 0.1 to 10 parts by weight of higher fatty acid triglyceride is mixed with 100 parts by weight of the raw material mixture, and the mixture is foam-molded. Method of manufacturing foam. (2) The conductive material according to claim 1, wherein the polyolefin resin is a plastic selected from the group consisting of polyethylene, polypropylene, ethylene-vinyl acetate copolymer, and mixtures thereof. A method for producing plastic foam.